This invention relates to a packing machine for feeding a band around a package such as a box or the like, drawing back the band to tighten it around the package while grasping a distal end of the band, bonding an overlapped portion of the band by welding or the like and cutting a portion of the band wound on the package from the remaining portion of the band, and more particularly to a band feeding and tightening apparatus provided on a packing machine and including plural pairs of rollers for carrying out feeding, drawing-back and tightening of a band.
A conventional packing machine is generally constructed so as to unwind a band from a reel on which the band is wound, feed the band to a pool box by means a pool feed roller and a pool touch roller arranged in a pair to temporarily pool it in the pool box, and then feed the band through a band feeding and tightening apparatus to a circumference of a package such as a box. Such feeding of the band to the circumference of the package is generally carried out employing, for example, an arch structure provided on a table on which the package is to be put. The arch structure and table each are formed therein with a band passage, so that the band may be circularly fed to the circumference of the package. Then, the band is clamped or grasped at a distal end thereof, followed by being drawn back by the rollers arranged in the band feeding and tightening apparatus. The arch structure and table each have a circular inner surface, which is formed with a slit; so that when application of band drawing-back force to the band fed into the arch structure and table causes the band to rush out of the slits, resulting in being wound around the package. The band is then tightened. Subsequently, the band is bonded at an overlapped portion thereof by welding or the like while being kept tightened. Thereafter, a portion of the band wound on the package is cut from the remaining portion of the band.
Now, such a conventional band feeding and tightening apparatus will be more specifically described with reference to FIG. 10. Feeding of a band is carried out by accessing feed touch rollers 35a and 35b through the band to a feed roller 31 rotated at a high speed. Drawing-back and tightening of the band is carried out by accessing a return touch roller 36 through the band to the return roller 33.
More particularly, the feed touch rollers 35a and 35b are pressedly contacted with the feed roller 31 while keeping a feed shaft 32 on which the feed roller 31 for feeding the band is fixedly mounted and a return shaft 34 on which the return roller 33 is fixedly mounted rotated through a differential speed reducer in directions opposite to each other, resulting in the band being fed. Drawing-back of the band is carried out by pressedly contacting the return touch roller 36 with the return roller 33. When the drawing-back is advanced to cause force applied to the return roller 33 by the band to reach a predetermined level, a clutch provided on the return shaft 34 starts to slip, resulting in rotation of the return shaft 34 being rapidly decreased. This causes the differential speed reducer to rotate the return roller 33 at a low speed and a high torque, so that tightening of the band may be accomplished.
The conventional band feeding and tightening apparatus thus constructed is disclosed in Japanese Patent Publication No 34051/1980 (55-34051), of which the disclosure is incorporated therein by reference.
In the conventional band feeding and tightening apparatus described above, the band is taken out of a pool box, passed through a guide chute 42 in which a band passage 41d is defined, and then fed to a space between the feed touch roller 35b and the feed roller 31 being rotated at a high speed. Then, the band is passed through a feed chute 38 in which a band passage 41c is defined and then passed between the return roller 33 and the return touch roller 36 which are kept separated from each other. Also, the band is passed through a band passage 41b defined between an outer periphery of the return roller 33 and an inside of a tension chute 37 and then fed to a space between the feed touch roller 35a and the feed roller 31 being rotated at a high speed. Thereafter, the band is passed through a return chute 39 in which a band passage 41a is defined and then fed to an arch structure (not shown).
Then, the band is grasped at a distal end thereof by a grasping unit (not shown). Then, the feed touch rollers 35a and 35b are separated from the feed roller 31 and the return roller 36 is pressedly contacted through the band with the return roller 33. This causes the band to be drawn back, resulting in rushing out of a slit of the arch structure and a slit of a table (not shown). Then, the return roller 33 tightens the band.
Unfortunately, the conventional band feeding and tightening apparatus constructed as described above often leads to jamming of the band in the band passages. More specifically, the band is caught in the band passages, resulting in being folded in a corrugated or crumpled manner in the band passages. The jamming is caused due to the reason that a distal end of the band is caught in the band passage when the band is unwound from a reel and fed to the band feeding and tightening apparatus at the time of starting the packing machine or due to the reason that the band is caught at an intermediate portion thereof in the band passage due to friction between the intermediate portion of the band and the band passage when the band is fed or drawn back at a high speed during running of the packing machine.
The jamming tends to readily occur when the band used lack firmness or nerve. Catching of the band in the band passage tends to occur at a boundary area between the band passages such as a boundary area between the guide chute and the tension chute, that between the tension chute and the return chute, or the like. Also, the catching readily occurs at a gap between the feed touch roller 35a or 35b and the guide chute 42 or return chute 39 when the feed touch rollers 35a and 35b are kept separated from the feed roller 31.
In addition, the conventional band feeding and tightening apparatus is so constructed that the band passage 41b of the tension chute 37 is formed into an increased width so as to prevent the band from contacting with the return roller 33 constantly rotated at a high speed in a direction opposite to the feed roller 31 when the band is being fed by the feed roller 31. Unfortunately, such construction exhibits a disadvantage that when the band is caused to unintendedly contact with the return roller 33, it is exposed to force applied thereto in a direction opposite to a direction of feeding of the band, resulting in jamming of the band in the band passage 41b increased in width.